Phylogentic Relationships of Living Amphibians Among Three Orders Based on the Mitochondrial tRNA Genes

To date,there still is lack of a general consensus regarding the phylogenetic relationships of three living orders of amphibian among herpetologists.The most widely accepted hypothesis is the monophyletic origin in the class Amphibia,which proposed a sistergroup relationship between Caudata and Anura (the Batrachia hypothesis) to the exclusion of the Gymnophiona.However,the phylogenetic relationship among living amphibians is still a controversial issue.The complete nucleotide sequence of the mitochondrial genome of Fejervarya limnocharis was detailedly compared with those of 6 other amphibians.The nucleotide sequences of 22 tRNA encoded by 7 amphibians mitochondrial genomes were combined and aligned to the homologous sequences of the 11 veterbrate taxa.Teleosts selected as outgroup,the phylogenetic analyses results show that MP and ML trees all strongly support the monophyly of living amphibians with respect to other living tetrapods and favor a sister group relationship for caecilians and urodeles.Robustness of our results was confirmed by high bootstrap support of all nodes in the trees.This result contradicts the Batrachia hypothesis,and is consistent with Bolt s hypothesis (1991) basing on the morphological data.The result was also supported by previous molecular studies based on the data from mitochondrial and nuclear rRNA genes.In addition,the reason for our result inconsistent with previous works and the shortcomings of phylogenetic analyses based on the complete mitochondrial genomes were also discussed.